实体框架:使用多个连接表

只有在以下情况下,EF才允许您使用隐式连接表:(1)它没有其他列;(2)它没有被其他实体引用,而不是被多对多关系的两端引用。

CompanyDepartment 满足条件(1),但不满足条件(2),因为它引用自 CompanyDepartmentBusinessUnit ,因此需要使用具有两个一对多关系的explcit实体。

一旦你这样做了,现在就可以看到 公司部门业务单元 满足这两个条件,因此可以使用隐式连接表建模 BusinessUnit 和 公司部门 .

话虽如此,最终的模型应该是这样的:

public class Company
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<CompanyDepartment> DepartmentLinks { get; set; }
}

public class Department
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<CompanyDepartment> CompanyLinks { get; set; }
}

public class BusinessUnit
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsPersonal { get; set; }
    public ICollection<CompanyDepartment> CompanyDepartments { get; set; }
}

public class CompanyDepartment
{
    public int CompanyId { get; set; }
    public int DepartmentId { get; set; }
    public Company Company { get; set; }
    public Department Department { get; set; }
    public ICollection<BusinessUnit> BusinessUnits { get; set; }
}

并考虑到默认EF约定,使用以下最小fluent配置:

modelBuilder.Entity<Company>().ToTable("Company");
modelBuilder.Entity<Department>().ToTable("Department");
modelBuilder.Entity<BusinessUnit>().ToTable("BusinessUnit");
modelBuilder.Entity<CompanyDepartment>().ToTable("CompanyDepartment");

modelBuilder.Entity<CompanyDepartment>()                
    .HasKey(e => new { e.CompanyId, e.DepartmentId });

modelBuilder.Entity<CompanyDepartment>()
    .HasMany(e => e.BusinessUnits)
    .WithMany(e => e.CompanyDepartments)
    .Map(m => m
        .MapLeftKey("CompanyId", "DepartmentId")
        .MapRightKey("BusinessUnitId")
        .ToTable("CompanyDepartmentBusinessUnit")
    );